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73 lines
2.9 KiB
73 lines
2.9 KiB
# frozen_string_literal: true
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module StatusSafeReblogInsert
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extend ActiveSupport::Concern
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class_methods do
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# This patch overwrites the built-in ActiveRecord `_insert_record` method to
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# ensure that no reblogs of discarded statuses are created, as this cannot be
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# enforced through DB constraints the same way as reblogs of deleted statuses
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#
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# We redefine the internal method responsible for issuing the `INSERT`
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# statement and replace the `INSERT INTO ... VALUES ...` query with an `INSERT
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# INTO ... SELECT ...` query with a `WHERE deleted_at IS NULL` clause on the
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# reblogged status to ensure consistency at the database level.
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#
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# The code is kept similar to ActiveRecord::Persistence code and calls it
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# directly when we are not handling a reblog.
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def _insert_record(values, returning)
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return super unless values.is_a?(Hash) && values['reblog_of_id']&.value.present?
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primary_key = self.primary_key
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primary_key_value = nil
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if prefetch_primary_key? && primary_key
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values[primary_key] ||= begin
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primary_key_value = next_sequence_value
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_default_attributes[primary_key].with_cast_value(primary_key_value)
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end
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end
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# The following line departs from stock ActiveRecord
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# Original code was:
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# im.insert(values.transform_keys { |name| arel_table[name] })
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# Instead, we use a custom builder when a reblog is happening:
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im = _compile_reblog_insert(values)
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connection.insert(im, "#{self} Create", primary_key || false, primary_key_value, returning: returning).tap do |result|
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# Since we are using SELECT instead of VALUES, a non-error `nil` return is possible.
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# For our purposes, it's equivalent to a foreign key constraint violation
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raise ActiveRecord::InvalidForeignKey, "(reblog_of_id)=(#{values['reblog_of_id'].value}) is not present in table \"statuses\"" if result.nil?
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end
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end
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def _compile_reblog_insert(values)
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# This is somewhat equivalent to the following code of ActiveRecord::Persistence:
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# `arel_table.compile_insert(_substitute_values(values))`
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# The main difference is that we use a `SELECT` instead of a `VALUES` clause,
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# which means we have to build the `SELECT` clause ourselves and do a bit more
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# manual work.
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# Instead of using Arel::InsertManager#values, we are going to use Arel::InsertManager#select
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im = Arel::InsertManager.new
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im.into(arel_table)
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binds = []
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reblog_bind = nil
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values.each do |name, attribute|
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attr = arel_table[name]
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bind = predicate_builder.build_bind_attribute(attr.name, attribute.value)
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im.columns << attr
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binds << bind
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reblog_bind = bind if name == 'reblog_of_id'
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end
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im.select(arel_table.where(arel_table[:id].eq(reblog_bind)).where(arel_table[:deleted_at].eq(nil)).project(*binds))
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im
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end
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end
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end
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